Syrian golden hamsters in the laboratory infected with this variant showed maximum body weight loss and higher viral load as against those who were infected with the B.1 lineage (D614G) of the virus. (File Photo/Representational) The Centre confirmed that the SARS-CoV2 variant B.1.617 (double mutant) could be the cause behind the surge, and now a new study at the Indian Council of Medical Research-National Institute of Virology ICMR-NIV has also flagged its pathogenic potential.
Syrian golden hamsters in the laboratory infected with this variant showed maximum body weight loss and higher viral load as against those who were infected with the B.1 lineage (D614G) of the virus.
Increased severity of B.1.617.1 infection in hamsters was demonstrated by the higher body weight reduction, lung viral load and more severe changes in the lungs as compared to that of B.1 (the first variant of SARS CoV-2, D614G), which had become dominant and is prevalent worldwide since March 2020, according to the study titled “SARS CoV-2 variant B.1.617.1 is highly pathogenic in hamsters than B.1 variant”, posted on May 5 in bioRxiv pre-print.
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Dr Pragya D Yadav, scientist ‘E’ and group leader, Maximum Containment Facility, Indian Council of Medical Research-National Institute of Virology, who is the first author of the paper, said the B.1.617 variant has eight amino acid changes in the spike region.
However, the evolution of multiple sub-lineages within B.1.617 lineage is a major concern. “Sub-lineages B.1.617.1, B.1.617.2 and B.1.617.3 have a different set of unique substitutions and deletions. The predominant lineage are the B.1.617.1 and B.1.617.3, and these are characterised by the presence of L452R, E484Q and P681R amino acid changes, while the B.1.617.2 lacks the E484Q mutation,” Dr Priya Abraham, one of the authors and Director of ICMR-NIV, said.
Scientists investigated the viral load and pathogenic potential of B.1.617.1 in Syrian golden hamsters. What they did was to compare two groups of Syrian golden hamsters (nine each) that were inoculated intranasally with SARS CoV-2 isolates, B.1 (D614G) and B.1.617.1 respectively.
The animals were monitored daily for the clinical signs and body weight. The necropsy (examination of animals after death) of three hamsters each was performed on 3, 5- and 7-days post-infection. Throat swab, nasal wash and organ samples (lungs, nasal turbinate, trachea) were collected and screened using SARS-CoV-2 specific Real- time RT-PCR.
Hamsters infected with B.1.617.1 demonstrated increased body weight loss compared to the B.1 variant. The highest viral load was observed in nasal turbinate and lung specimens of animals infected with B.1.167.1 on third day post infection.
Gross examination of lung specimens showed pronounced congestion and hemorrhages on the fifth and seventh day post infection in the case of the B.1.617.1 as compared with the B.1.
The origin of this variant is still unknown and the presence of this variant has been identified not only in India but from 21 different countries.
According to the data from the National Centre for Disease Control, of 13,000 samples sequenced, 3,532 were found to have variants of concern and of these, 1,527 had the B.1.617 variant.
The current surge in cases over the past one-and-a-half months in some states has shown a correlation with rise in the B.1.617 lineage, Dr Sujeet Singh, director, NCDC, said at a press briefing.
Recent studies have shown that Covaxin (a whole virion inactivated vaccine) works against the B.1.617 variant.
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